Manufacture of water-resistant laminated articles



?atented Jan. 14, 1947 UNl'lED STATESPATENT crin -cs zg tiaaeo M AN UFACTURE OF WATER-RESISTANT LAMINATED ARTICLES fi I John D. Carter, Lansdowne, Pa., assignor to I r Quartz Company, Philadelphia, l

Pa., t corporation of Pennsylvania No Drawing. Application August 1,1941, l

Philadelphia Serial No. 405,119

This invention relates to manufacture of we.- tar-resistant laminated articles; and it comprises a process of making substantially water-proof laminated paper board, corrugated paper and sim ilar articles, in which plies of porous material,

such as paper are united. with silicate adhesives,

;said process comprising the step of impregnating V the porous material, where it comesin contact with said silicate adhesive, with aluminum chloride in proportions sufficient to insolubilize the adhesive bond, said proportions being usually also suflicient to prevent desizing of the plies by alkali derived from said adhesive, said impreg-' nating step, being followed by combining the plies with the use of a silicate adhesive in the usual manner. The invention-also includes the water-resistant articles made by the process described, these articles being composed of plies of fibrous material united witha bond comprising also true that, in-the case. of certain unusually severe conditions of use, such as are met in the shipment of wet vegetables and the export shipment of canned goods' which are expected to be exposed to the weather for extended periodsv of time, the bond produced by the usual silicate adhesives is not satisfactorily water-proof.

13 Claims. (01. 154-40) it t I on either surface with heavy metal or alkaline earth metal salts in order to prevent the migration of alkali through the plies and the consequent staining of the facing sheets, while in the later patent the use of ammonium salts is recommended for the same purpose. But the salts listed in these patents, when applied in the manner disclosed, have insufficient effect; upon the water solubility of the silicate bondsfl hence articles made in accordance with thei dlrections given in these patents tend to fail in'the above tests owing to the separation of the plies on immersion.

I have now found that, if the faces of the plies to united are impregnated with aluminum chloride prior to combining them. not only is desizing prevented but also separation of the plies on immersion is substantially l prevented;-

The silicate bonds produced are-substantially insoluble in water. In a large number of tests which were designed to find other salts which might produce the same results, none was found which was capable of producing results as satisfactory as those produced by aluminum chloride.

This salt is apparently unique in this respect. Surprisingly neither aluminum sulfate" nor aluminum nitrate is effective, which indicates that the effect is not specific to the aluminum ion. And

magnesium and zinc chlorides, whilerprcducing a slight water-insolubilizing effect on the adhesive bond, are not comparable in effect to aluminum chloride, which indicates that this, effect is also not specific to the chloride ion. Ammonium salts were found to produce no substantial insolubilizing effect on the silicate bond in spite of the fact that these salts afford adequatei; protection against desizing. There appears to he no direct Specifications have recently been drawn up tion of plies caused during, an immersion of 1 hour must not exceed 2 inches at any point. Combined board made with the usual silicate adhesive is not usually able to pass such rigid requirements. The production of insoluble silicate bonds capable of withstanding water-immersion tests for all types of servic has, of"

course, long been a desideratum in the art.

The problem of preventing, desizlng by the alkali derived from silicate adhesives has been solved with satisfaction by methods which are described in my two prior patents, Numbers 2,015,359 and 2,231,562. In the former patent it is recommended that the plies to be united betreated relationship between these two effects.

In comparison with the specifications given above, in which the adhesive bond is required to withstand immersion for 1 hourwithout producing a separation of the plies greater than 2 inches, I have found that compound paperboard made with my new water insoluble bond will withstand immersion for periods up to four weeks or longer which, needless to say, is a highly surprising result. Test pieces produced under optimum conditions of impregnation were found to have their bonds-substantially unimpaired after four or six proportions of aluminum chloride and silicate to dium chloride, magnesium chloride etc. lieved that the active agent in these mixtures is produce an insoluble bond. The best proportion in a given case depends, of course, upon the porosity of the paper, since a porous paper requires a larger application of aluminum chloride to produce a given concentration at its surface.

" I have found, however, that for heavily sized, and

therefore substantially non-porous papers, best results have been obtained when the ratio between the aluminum chloride and the silicatein the joint, expressed in molecular proportions, fallswithin the range of about 1AlCl::3SiO2 to lAlClatlOSiOz, The range over which improved results are obtained for papers in general extends from about, 1AlCla:1Si02 to 1A1Cls220SiO2. An excess of AlCla over that represented by the ratio of about 1AlCl:;:2SiOz is not detrimental but it does not appear to increase the insolubility of the bond appreciably. These figures include the aluminum chloride applied to the adjacent faces of both plies forming the joint.

It'is relatively easier to determine the best pro portions of aluminum chloride to prevent desizing in the case of plies which are sized with sizing agents subject to attack by alkalls. I have found that, for complete protection against desizing, it is necessary that the chloride ion of the aluminum chloride be approximately equivalent to or slightly in excess of the sodium ion ofthe adhesive present in the joint. The protection against desizing falls-oi! rather rapidly when the ratio of the chloride ion of the sodium ion .falls below a ratio of about 1C1 to lNa, although some protection is obtained at ratios as low as 101 to 2.5 NazO. An excess of aluminum chloride does no harm but, when the ratio exceeds about 2C1 to, lNa, no improvement in the. pro tection ls observable, Since the prevention of desizing is of great importance in the production of a water-resistant article, I prefer to employ the aluminum chloride and silicate in proportions such that the best desizing action is obtained.

Although I believe it best to use aluminum chloride per se in the process of the present invention, I have found that substantially the same results are produced by the use of mixtures of chemicals capable of forming aluminum chloride in solution. Thus, it is possible to mix aluminum sulfate and other soluble aluminum salts with water soluble chlorides, such as ammonium chloride, so- It is bethe aluminum chloride which is formed by chemical reaction.- This procedure, therefore, represents an alternative embodiment of this inven tion.

It is possible to add various addition agents to the aluminum chloride impregnating solutions which are adapted to accomplish certain special results. rosion inhibitors, such as dlchromates or aniline For-example it is possible to add cor oil. Any other agents which are compatible with the aluminum chloride can be incorporated. It is also possible to employ separately applied agents to prevent desizing in connection with my process.

, It is possible, for example, to apply a solution of an ammonium salt to the outer faces of a laminated article while applying aluminum chloride to the ply faces which are bonded.

The aluminum chloride is advantageously applied to the plies in the form of an aqueous solution but any other method adapted to impregnate uniformly the surface layers of the plies is equally aluminum chloride can be applied to the finished plies by brushing or spraying operation, or it may be applied by means of transfer rolls of the type used for applying adhesives in machines for the continuous manufacture of corrugated or combined paper board. It is more convenient, however, to apply-the aluminum chloride during the paper making process, for example by means of the calender rolls of the paper machine, in a man,

ner analogous to that used inproducing the water-finishing of'paper.

The concentration of the aluminum chloride solution to be employed depends,.of course, upon the method of application. Other factors being equal, it is usuallyadvantageous to employ solutions which are concentrated and nearlysaturated for the reason that there is then less water to eliminate in later operations' When an aqueous solution is applied on the calender rolls of a paper making machine,.a. concentrationranging from about'lo to 50 per cent canibe employed, for

u example.

Ina specific example of the present invention, which represented apractical embodiment, an aluminum chloride solution was used which contained 162 pounds AlCli-fiHzO and 0.16 pound sodium dichromate per gallons of solution.

This solutionwas applied to both faces of chip stock on the calender rolls of a paper making machine, the average application amounting to 1.08 pounds of AiCh-6H2O pe 1000 square feet. 1

The back faces of two jute liners were also I treated with an aluminum chloride solution in similar manner, the'average application amounting to 0.476'pound per 1000 squarefeet. These treated plies were combined into a solid board having a thickness of 0.1 inch, using a silicate adhesive containing 9.1 per cent NazOand 29.9

per cent SiOz.

The finished board thus produced was tested for water resistance in comparison with uncom- -bined liner and chip stock as well as against untreated combined board. It was found. that, after 2% hours immersion in water,v the un combined, untreated chip stock showed a water pick-11p of 35.5 per cent. while the uncombined,

untreated liners gave a water pick-up of 43- per water pick-up of 56.8 per cent whereas the,

smaller scale, a solution of aluminum chloride,

efiective. Thus, it is possible to employ solutions of aluminum chloride in organic solvents, such as carbon tetrachloride, for example. Solutions of containing 2 parts by weight of the crystallized salt to 10 parts of water, was applied to plies of paper stock well-sized with rosin. After the solution haddried, the plies were combined by means of a sodium silicate solution, testing approximately 405 B., and containing about 8.9%

NazO and 28.5% SiOz. After air-drying, test samples of 'the'combined board were placed inwater, at room temperature. After soaking for 4 weeks and drying, the bond'was still good. The samples showed no desizing by alkali from the adhesive. i

In a third specific example, plies of a paper stock well-sized with rosin were treated on one substantially of an alkali metal a substantially insolu a) a solution of aluminum chloride compialir arts of crystallized aluminum sulfate and 1. part of sodium chloride to parts of water. These plies were combined with the use of an adhesive made from asilicatc solution containing about 8.9% N320 and 28.5% SiOz, which solution was diluted to a gravity of 34 B. and then mixedwith hydrous clay in the proportion of about 100 parts of the diluted solution to 30 parts of the clay. Test samples or the combined board showed complete protection against desizing by alkali from the adhesive and, when immersed in Water for 18 hours, showed no weakening of the bond.

While I have described what I consider to be the best embodiments of my invention, it is evident, of course, that many modifications can be made in the specific procedures which have 'been mentioned without departing from the purview of this invention. My invention is broadly applicable to the uniting of porous materials of all types by means of alkali metal silicate adhesives I in general. It may be used in making ply-wood,

for example, with silicate adhesives and corrugated as well as solid articles. Any of the conventional silicate adhesives can be employed in my invention with the resultant formation of substantially insoluble bonds. Further modifications which fall within the scope of the following claims will be immediately evident to those skilled in this art. I

What I claim is: 1. In the manufacture of laminated products from plies" of porous material, the process which comprises/impregnating the faces of the plies to be joined with a small amountof aluminum chloride, applying a. silicateadhesive and combining the plies whereby a substantially insoluble silicate bond is produced.

2. In the manufacture of laminated products from plies of porous material, the process which comprises applying to the faces of the plies to be joined a small'amount of a concentrated solution containing aluminum chloride. drying and then uniting the plies with the aid of a silicate adhesive the bonding agent in which consists silicate, whereby le silicate bond is produced.

3. The process of claim 2 wherein said aluminum chloride solution contains a corrosion inhibitor compatible with the aluminum chloride.

4. The process of claim 2 wherein said aluminum chloride solution is formed by mixing aluminum sulfate with a soluble chloride, whereby the aluminum chloride is formed by double decomposition.

5. In the manufacture of laminated products from plies of porous material, the process which comprises applying to the faces of the plies to be united a concentrated aqueous solution of aluminum chloride, drying and combining the plies with the aid of a sodium silicate adhesive the bonding agent in which consists substantially of sodium silicate, the aluminum chloride being employed at least in sufilcient quantity, relative to the NazO in the adhesive in the joint, to produce a molecular ratio of about 1.101 to lNarO.

7. A laminated article formed of piles of porous material united by a substantially insoluble sill. cate bond comprising the reaction products of an alkali metal silicate and aluminum chloride, said reaction products being formed in situ.

8. A laminated article formed of plies of a porous material united by a substantially insoluble silicat bond comprisin the reaction productspf an alkali metal silicate, aluminum su'l fate and a soluble chloride, said reaction products being formed in situ.

9. A laminated article formed of plies of fibrous material sized with a sizing attack by alkali and united by a substantially insoluble silicate bond comprising the reaction products formed in situ of an alkali metal silicate adhesive, in which the bonding agent consists substantially of an alkali metal silicate, and aluminum chloride, said article being substantially proof against desizing caused by alkali derived from said alkali metal silicate.

10. A laminated article formed of parts of fibrous material sized with a sizing agent subject plies with the aid of asilicate adhesive the bondwhich the bonding agent consists substantially to attack by alkali and united by a substantially insoluble silicate bond comprising the reaction products formed in situof a silicate adhesive, in which the bonding agent consists substantially of sodium silicate, and aluminum chloride, the molecular ratio of Cl to'Na2O in said bond being at least about 1.1 to 1, said article being substantially proof against desizlng caused by alkali derived from said alkali metal adhesive.

12. A combined paper board formed of paper plies sized with a sizing agent subject to attack by alkali and combined by a silicate adhesive bond, said bond comprising the reaction products formed in situ of a silicate adhesive, in which the bonding agent consists substantially of sodium silicate, and aluminum chloride, said reaction products rendering said board water resistant as well as proof against desizing caused from the alkali of said adhesive.

13. A combined paper board formed of paper plies sized with a sizing agent subject to attack byalkali and combined by a silicate adhesive bond, said bond comprising the reaction residues formed in situ of a silicate adhesive, in

of sodium silicate, aluminum sulfate and a so1- uble chloride, said reaction products making said bond substantially insoluble and rendering said board substantially proof against desizing caused from the alkali of said adhesives.

JOHN D. CARTER.

agent subject to 

